I know that the admins and developers sometimes announce what the future changes will be like, at least in a few words, I am interested whether they said something about ship stats, particularly the storage capacities, kg and m3. Has anything been said about that? Is a big change planned, or maybe they said, they are not going to touch this part of the stats?

Nothing has ever been stated to that effect. Obviously if something is found to not make sense in the future given the development direction of the game then it may be changed, but there's no guarantee of any "warning" ahead of time.

They are subject to change when stats are balanced for combat. They may not change at all, but then again, they may, so don't go into the situation with specific expectations. |: It depends on what they decide will be needed or desired. Warnings are unlikely but possible, depending on how well in advance the devs decide prior to the actual implementation.

Basically, all things are uncertain, save for uncertainty itself. Welcome to SWC. :p